18.04 - Adding repository via terminal results in "add-apt: command not found" error

Every time I do anything I do anything related to sudo (mostly installing repositories), it says command not found.

I type:

sudo add apt-repository ppa:ppsspp/stable

It then says

sudo:add-apt: command not found

Sometimes it tells me to manually run configure --a, which I do, and it still doesn't work. Anyone know how to fix???

I'm on Ubuntu 18.04 LTS

The command is add-apt-repository, you're missing the second hyphen.